# [PYTHON MATRIX-SIG] RubberIndex

**David Ascher
**
da@maigret.cog.brown.edu

*Mon, 12 Feb 1996 22:39:01 -0500 (EST)*

I'm still trying to figure out the ... index. If I understand
correctly, it stands for "however many ':' I need depending on the rank
of the object I'm indexing, so that the indices I *do* specify are at the
end of the index list as opposed to the usual beginning.
So, if I have a rank-3 array A, then
A[...,0]
is the same thing as
A[:,:,0]
but if B is rank-4, then
B[...,0]
is the same thing as:
B[:,:,:,0]
This "stretching" only works from the left: In other words, if '...' is
used *after* a non-pseudo index, then it is equivalent to ':', and does
not stretch. [should ... be allowed after a non-pseudo index?]
If C is a rank-5 array, then
C[...,0,...]
is the same thing as
C[...,0,:]
and
C[:,:,:,0,:]
but NOT:
C[:,:,0,:,:]
This seems to work with my test cases. Am I missing some key
functionality?
--david
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